Re: [PATCH 1/2] [gdb/testsuite] Fix timeout in do_self_tests

[Thiago Jung Bauermann <thiago.bauermann@linaro.org>]

Tom de Vries <tdevries@suse.de> writes:

> I noticed a patch reporting a timeout in the selftests on slow systems [1].
>
> I tried to see if I could trigger some timeouts.
>
> With the following setup:
> - gdb build with -O0
> - running gdb.gdb/*.exp
> - aarch64-linux platform
> - all cpu threads set to the lowest value: 600 Mhz
> - taskset -c 0
> I managed to trigger timeouts in the form of warnings:
> ...
> (gdb) set height 0
> WARNING: Couldn't set the height to 0
> set width 0
> WARNING: Couldn't set the width to 0.
> break main
> (gdb) set width 0
> (gdb) break main
> Breakpoint 1 at 0x41767c: file gdb.c, line 30.
> (gdb)
> ...
> in both gdb.gdb/selftest.exp and gdb.gdb/python-helper.exp.
>
> Note that this is extra slow because the default worker-threads is set using
> std::thread::hardware_concurrency, which is 8 even though we use taskset -c 0:
> ...
> $ taskset -c 0 gdb -q -batch -ex "maint show worker-thread"
> The number of worker threads GDB can use is the default (currently 8).
> ...
> making 8 worker threads compete for 1 cpu thread.
>
> The timeouts are triggered in do_self_tests by gdb loading the symbols in the
> background, making the effort to do so overlap with subsequent commands.
>
> Fix this using "maintenance set dwarf synchronous on".
>
> [1] https://sourceware.org/pipermail/gdb-patches/2026-September/230133.html
> ---
>  gdb/testsuite/lib/selftest-support.exp | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

I also see the timeouts above in gdb.gdb/python-helper.exp with an
especially slow setup that I use sometimes: running the GDB testsuite in
a QEMU TCG aarch64 VM on an old x86_64 server. And this patch solves
them.

This is with GDB built with -O0, but as I mentioned in an email to Simon
perhaps I should switch to -Og. I still have to check how much of a
difference it makes.

I don't see the timeouts on a QEMU TCG aarch64 VM running on my faster
x86_64 laptop, though.

Also, when I run the testsuite on the slow setup I normally generously
increate gdb_test_timeout.

All this to say that I see value in this patch, but it's somewhat niche.

If you do decide to apply it:

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Tested-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>

-- 
Thiago
(he/him)